Study of lossy effects on the characteristics of axially slotted circular or elliptical cylindrical antennas coated with metamaterials

The radiation properties of an axially slotted circular or elliptical antenna coated with lossy metamaterials are studied. The fields inside and outside the dielectric coating are expressed in terms of complex Mathieu functions. The boundary conditions at various surfaces are enforced to obtain the unknown field expansion coefficients. Numerical results are presented graphically for the radiation pattern, aperture conductance and antenna gain for the TM case. It was found that a slotted antenna coated with lossy metamaterials has a more directional beam with lower sidelobes compared to one coated with conventional dielectric material or lossless metamaterials.